Preheat your oven to 220°C(200°C fan assisted). Grease and line a 23x13x7cm loaf tin with baking paper.
Combine the polenta, bread flour, caster sugar, baking powder and salt in a large bowl.
Whisk together the eggs and milk then pour in the melted butter and keep whisking until they're combined.
Pour in the wet ingredients and mix until they're just combine. Be careful not to overmix at this point, but make sure there are no dry patches.
Stir through the spring onions, jalapeño peppers and sweetcorn.
Pour the mixture into the prepared loaf tin and leave to rest for 10 minutes.
Transfer the tin to the middle shelf of your preheated oven and bake for 10 minutes.
At this point, lower the temperature to 200°C(180°C fan assisted) and bake for another 20-25 minutes. It should be golden brown on top and a skewer inserted into the middle will come out clean.
Place the tin on a wire rack and leave to cool for 5 minutes before turning the loaf out and leaving to cool completely.